System and method for high power diode based additive manufacturing

ABSTRACT

The present disclosure relates to a system for performing an Additive Manufacturing (AM) fabrication process on a powdered material (PM) forming a substrate. The system uses a first optical subsystem to generate an optical signal comprised of electromagnetic (EM) radiation sufficient to melt or sinter a PM of the substrate. The first optical subsystem is controlled to generate a plurality of different power density levels, with a specific one being selected based on a specific PM forming a powder bed being used to form a 3D part. At least one processor controls the first optical subsystem and adjusts a power density level of the optical signal, taking into account a composition of the PM. A second optical subsystem receives the optical signal from the first optical subsystem and controls the optical signal to help facilitate melting of the PM in a layer-by-layer sequence of operations.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/145,402, filed May 3, 2016, which is a continuation of U.S. patentapplication Ser. No. 14/988,190, filed Jan. 5, 2016 (now U.S. Pat. No.9,855,625), which is a divisional of U.S. patent application Ser. No.13/785,484, filed on Mar. 5, 2013 (now U.S. Pat. No. 9,308,583). Thisapplication claims the benefit and priority of each of the aboveapplications, and the disclosures of all of the above applications areincorporated herein by reference.

STATEMENT OF GOVERNMENT RIGHTS

The United States Government has rights in this invention pursuant toContract No. DE-AC52-07NA27344 between the U.S. Department of Energy andLawrence Livermore National Security, LLC, for the operation of LawrenceLivermore National Laboratory.

FIELD

The present disclosure relates to Additive Manufacturing systems andtechniques for making three dimensional articles and parts, and moreparticularly to a system and method for performing AdditiveManufacturing using a high power diode system.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Additive Manufacturing (“AM”), also referred to as 3D printing, is amanufacturing technique in which material is added sequentially, layerby layer, in order to build a part. This is in contrast to traditionalmachining, where the part starts as a block of material that is thenwhittled down to the final desired shape. With AM fabrication, adirected power source is used to agglomerate material (typically powder)into a final, near net-shape article. Three dimensional articles aremanufactured one layer at a time as an assemblage of two-dimensionalsections. One important advantage of AM fabrication is that complexshapes (e.g. parts with internal features) can be realized. Anotherimportant advantage is that the material required is limited to thatused to form the final part. Thus, AM fabrication has the benefit ofvery little material loss. This is especially important forexpensive/tightly controlled materials.

The use of AM for metal fabrication is relatively recent. Historically,plastics have been the focus of commercial systems that employ AM.Nevertheless, the use of metals with AM is highly commercially andtechnologically important because the majority of engineered structuresrely heavily on metals. Metal AM requires a relatively high power,highly focused laser beam (typically on the order of 100 W-1000 W) tomelt, fuse, and/or sinter metallic powder. The metal powder is typicallyplaced in a powder bed during the AM process. The laser beam is rasteredalong the powder surface to make a two-dimensional section per pass.Once each layer is completed, the powder bed retracts and new powder islayered on top of the just-completed layer. Considering that a typicallayer thickness is only about 50-100 microns, it can be seen how thisrastering is the most time consuming step. This is the principal reasonwhy objects that would only take two to three hours to machine usingtraditional machining methods may take up to eight hours or more usingAM. Moreover, due to the necessity of rastering the laser beam, themaximum part size can be limited. Presently a 25 cm×25 cm area part sizeis the largest part size that can be made with an AM technique thatinvolves rastering the laser beam. Accordingly, there is a strong desireto reduce the time required to manufacture objects, and particularlymetal objects, using AM. One important challenge that the presentdisclosure addresses is overcoming this relatively slow speednecessitated by the raster scanning operation employed with aconventional AM fabrication process.

SUMMARY

In one aspect the present disclosure relates to a system for performingan Additive Manufacturing (AM) fabrication process on a powderedmaterial forming a substrate. The system may comprise a first opticalsubsystem for generating an optical signal comprised of electromagneticradiation sufficient to melt or sinter a powdered material of thesubstrate. The first optical subsystem may be controllable so as togenerate a plurality of different power density levels, with a specificone of the power density levels being selectable based on a specificmaterial forming a powder bed being used to form a 3D part. The firstoptical subsystem is able to generate the electromagnetic radiation withan average power density level of greater than 200 W/cm² over theduration of the signal, and produces a beam having an area sufficient toilluminate at least a portion of the powdered material and to melt thepowdered material. The system further may include at least one processorwhich dynamically controls the first optical subsystem, and isconfigured to adjust a power density level of the optical signal takinginto account a composition of the powdered material. The system mayfurther include a second optical subsystem arranged upstream of thepowdered material, and downstream of the first optical subsystem,relative to a direction of travel of the optical signal. The secondoptical subsystem may be configured to receive the optical signal fromthe first optical subsystem and to provide control over optical signalto help facilitate melting of the powdered material in a layer by layersequence of operations.

In another aspect the present disclosure relates to a method forperforming an Additive Manufacturing (AM) fabrication process on apowdered material forming a substrate. The method may comprise using afirst optical subsystem for generating an optical signal comprised ofelectromagnetic radiation sufficient to melt or sinter a powderedmaterial of the substrate; the first optical subsystem being controlledso as to generate a plurality of different power density levels, with aspecific one of the power density levels being selectable based on aspecific material forming a powder bed being used to form a 3D part. Thefirst optical subsystem is able to generate the electromagneticradiation with an average power density level of greater than 200 W/cm²over the duration of the signal, and produces a beam having an areasufficient to illuminate at least a portion of the powdered material andto melt the powdered material. The method may further include using atleast one processor to dynamically control the first optical subsystem,and to adjust a power density level of the optical signal taking intoaccount a composition of the powdered material. The method may furtherinclude using a second optical subsystem arranged upstream of thepowdered material, and downstream of the first optical subsystem,relative to a direction of travel of the optical signal, to receive theoptical signal from the first optical subsystem and to provide controlover the optical signal to help facilitate melting of the powderedmaterial in a layer by layer sequence of operations.

In still another aspect the present disclosure relates to an apparatusfor performing an Additive Manufacturing (AM) fabrication process on apowdered material forming a substrate. The apparatus may comprise alaser source for generating a laser beam, an optical subsystem forshaping the laser beam into at least one line segment directed at thepowdered material, and at least one processor. The laser source is ableto generate the electromagnetic radiation with an average power densitylevel of greater than 200 W/cm² to provide sufficient power to melt thepowdered material. The at least one processor controls at least one ofthe laser source or the optical subsystem to adjust a power densitylevel of the laser beam. The line segment of the laser beam is used tomelt different linear segments of the powdered material, and repeats themelting of additional linear segments of powdered material in alayer-by-layer sequence of operations using successively melted layersof the powdered material to form an additively manufactured part.

In still another aspect the present disclosure relates to an apparatusfor performing an Additive Manufacturing (AM) fabrication process on apowdered material forming a substrate. The apparatus may comprise anoptical subsystem including at least one laser source for producing aplurality of simultaneously generated laser beam line segments directedat the powdered material. The laser source is able to generate the laserbeam with an average power density level of greater than 200 W/cm² whichprovides sufficient power to melt the powdered material. At least oneprocessor may be included which controls the optical subsystem to helpadjust a power density level of the laser beam line segments. The laserbeam line segments are used to simultaneously melt different linearsegments of the powdered material, and the melting of different linearsegments is repeated in a layer-by-layer sequence of operations usingsuccessively melted layers of the powdered material to form anadditively manufactured part.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way. Inthe drawings:

FIG. 1 is a diagrammatic view of one embodiment of the present systemand method for performing an Additive Manufacturing (“AM”) fabricationprocess using a high power diode array and a mask;

FIG. 2 is a diagrammatic side view of the system of FIG. 1 showing how aportion of the optical rays from the diode array are reflected by apolarizing mirror during the fabrication process to prevent them fromreaching the substrate;

FIG. 3 is a chart illustrating the average power flux required to meltvarious types of metals;

FIG. 4 is a graph that shows a plurality of curves representing varioustemperatures required to melt various materials, along with the timerequired to melt each material;

FIG. 5 shows an alternative form of the system of the present disclosurein which distinct “tiles” (predetermined areas) corresponding to pixelsof the substrate are digitally controlled during the AM fabricationprocess;

FIG. 6 is another alternative form of the system of the presentdisclosure in which a plurality of focusing lenses are used tosimultaneously focus the output from the diode array onto specificsections of the substrate for simultaneously melting distinct, separatesheets of material; and

FIG. 7 is a diagrammatic side view of a method of deposition ofdifferent material types in powder form prior to illumination by diodearray generated light to melt/sinter the dissimilar powders together.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

Referring to FIG. 1 a system 10 is shown in accordance with oneembodiment of the present disclosure for performing an AdditiveManufacturing (“AM”) fabrication process. The system 10 may include ahigh power diode array 12 and a computer controlled, selective area mask14 (hereinafter simply “mask 14”). A suitable power supply 16 may beused for providing electrical power to the diode array 12. A computer 18or other suitable form of processor or controller may be used forcontrolling the power supply 16 to control the on/off application ofpower to the diode array 12 as well as selectively (i.e., digitally)controlling the mask 14 and shaping or focusing the optical beam.Optionally, separate processors or computers may be used to control thediode array 12 and the mask 14. Selectively electronically controllingthe mask 14 with the computer 18 allows the optical beam from the diodearray 12 to be prevented from reaching specific selected portions ofpowder that forms a substrate 20 (i.e., powder bed) so that thoseportions are irradiated by the beam. In FIG. 1 portion 15 is crosshatched to represent a portion of the output from the diode array 12that does not reach the powdered material of the substrate 20.

In one preferred form the diode array 12 may comprise a single largediode bar. Alternatively a plurality of diode bars located adjacent oneanother may be used to form the diode array 12. In one preferred formthe diode array may be made up of arrays of diode bars each being about1 cm×0.015 cm to construct a 25 cm×25 cm diode array. However, anynumber of diode bars may be used, and the precise number andconfiguration may depend on the part being constructed as well as otherfactors. Suitable diode bars for forming the diode array 12 areavailable from Lasertel of Tucson, Ariz., Oclaro Inc. of San Jose,Calif., nLight Corp. of Vancouver, Wash., Quantel Inc. of New York,N.Y., DILAS Diode Laser, Inc. of Tucson, Ariz., and Jenoptik AG of Jena,Germany, as well as many others. The diode array 12 is able to provide aminimum power density of about 10 kW/cm² and maximum>100 kW/cm² at twopercent duty cycle. This makes it feasible to generate sufficientoptical power to melt a wide variety of materials. FIG. 3 provides atable of the average power flux that has been calculated to melt varioustypes of materials. FIG. 4 shows a graph that illustrates theeffectiveness of the diode array 12 on a variety of metal powders (i.e.,Aluminum, Titanium, Iron and Tungsten), at a power flux sufficient tomelt all the materials. The calculations to obtain the graphs shown inFIG. 4 were performed in MATLAB with conductive and radiative lossestaken into account. A conservative 30% absorptivity was assumed alongwith a powder layer thickness of 100 μm.

It will also be appreciated that a significant advantage of using adiode array comprised of one or more diode bars is that such an assemblyis readily scalable. Thus, diode arrays of various sizes can beconstructed to meet the needs of making a specific sized part. Forexample, the diode array 12 may be constructed to have a one squaremeter area, which would allow correspondingly large scale components tobe constructed through an AM fabrication process, provided of coursethat a suitably sized powder bed is available to support fabrication ofthe part. Another significant advantage is that the system 10 can beintegrated into existing AM fabrication systems with the added benefitof no moving parts. The system 10 allows for the AM fabrication oftraditionally difficult to fabricate and join metal such as ODS (oxidedispersion strengthened) steels or any alloy traditionally formed usingsolid state (i.e., non-melt) processing techniques.

Referring to FIG. 2, in one preferred form the mask 14 forms a “liquidcrystal polarization rotator” comprised of a liquid crystal module (LCM)14 a and a polarizing mirror 14 b, in this example a polarizing mirror(hereinafter “polarizing mirror” 14 b). The polarizing mirror 14 bdirects the light defined by the liquid crystal polarization rotator andshapes the optical pattern that irradiates the substrate 20. The LCM 14a that helps to form the mask 14 may be made up of one or more twodimensional, electronically (i.e., digitally) addressable arrays ofpixels. Liquid crystal polarizers are commercially available and formtwo dimensional arrays of addressable pixels which work by changing thepolarity of an incoming photon that is then rejected by a polarizationelement. However, with the system 10, the polarizing mirror 14 b mayform a discrete component of the mask 14 that may be used to help focusand/or shape the optical signal.

In FIG. 2 the mask 14 receives light 22 being output from the diodearray 12 as the light irradiates the LCM 14 a. Pixels of the LCM 14 aare independently addressed using the computer 18 to reject light atspecific select areas of the substrate 20. Using the LCM 14 a and thepolarizing mirror 14 b to form the mask 14 enables the light generatedby the diode array 12 to be controllably directed onto only selectedareas of the substrate 20 as needed. In FIG. 2 light indicated by lines22 a is able to pass through the polarizing mirror 14 b while lightindicated by lines 22 b is rejected by the polarizing mirror. Animportant advantage of using a computer controlled LCM 14 a is that onlya very small amount of optical energy is absorbed into the polarizingmirror 14 b, thus making it feasible to prevent damage to the mirror.

During an actual AM fabrication operation, a first layer of powderedmaterial may be acted on by the system by pulsing the diode array 12 tomelt selected portions (or possibly the entire portion) of the firstlayer. A subsequent (i.e., second) layer of powdered material may thenbe added over the layer just acted on by the system 10 and the processwould be repeated. The diode array 12 may be pulsed to melt one or moreselected subportions (or possibly the entirety) of the second layer ofmaterial. With each layer the system 10 electronically controls thepixels of the mask 14 to selectively block specific, predeterminedportions of the substrate 20 from being irradiated by the pulsed opticalsignal from the diode array 12. This process is repeated for each layer,with the computer 18 controlling the mask 14 so that, for each layer,one or more selected subportions (or possibly the entirety) of thepowdered material is blocked by the mask 14 from being exposed to thepulsed optical signal. Preferably, an entire two dimensional area ofeach layer is melted or sintered at once by pulsing the diode array 12.However, it is just as feasible to raster scan the diode array 12 overthe two dimensional area in the event the entire two dimensional areacannot be completely irradiated by the diode array.

An alternative to the addressable mask 14 is a non-addressable mask. Anon-addressable mask may be a precision cut piece of metal (e.g.,tungsten) that would simply block portions of the light beam. While sucha machined mask can be used to build simple geometries, the fullpotential of the system 10 described herein will be maximized if anaddressable mask such as mask 14 is used.

Referring to FIGS. 5 and 6, two alternative systems 100 and 200 inaccordance with additional implementations of the present disclosure areshown. System 100 includes a diode array 102 and a diode relay telescope104. The diode relay telescope 104 is used to provide digital controlover “tiles” within an array image to the “pixels” in the substrate 20(powder bed). FIG. 6 illustrates a system 200 having a diode array 202and a plurality of focusing lenses 206 that are used to focus theoptical energy from the array onto a corresponding plurality of “sheets”representing the substrate 20.

The systems 10, 100 and 200 are able to melt and sinter each layer in asingle “pass” or, put differently, in a single operation by pulsing thediode array 12. The need to raster scan an optical beam dozens, hundredsor more times, back and forth across a surface, is therefore eliminated.This significantly reduces the time required to melt and sinter eachlayer of powder material during the AM fabrication process.

Referring to FIG. 7, a method of deposition of different material typesin powder form is illustrated in system 300. Nozzles 301, 302, and 303are capable of depositing layers of different material powders 304 ontothe substrate 20. The nozzle heads 301, 302 and 303 are rastered acrossthe part surface covering it with material addressed by a programmablesource. Both the irradiation from the diode array 12 and operation ofthe mask 14, as described in connection with the system 10, can becontrolled such that each material deposited from the nozzles 301, 302and 303 receives the correct amount of optical energy for a controlledmelt or sintering.

While various embodiments have been described, those skilled in the artwill recognize modifications or variations which might be made withoutdeparting from the present disclosure. The examples illustrate thevarious embodiments and are not intended to limit the presentdisclosure. Therefore, the description and claims should be interpretedliberally with only such limitation as is necessary in view of thepertinent prior art.

What is claimed is:
 1. A system for performing an Additive Manufacturing(AM) fabrication process on a powdered material forming a substrate, thesystem comprising: a first optical subsystem for generating an opticalsignal comprised of electromagnetic radiation sufficient to melt orsinter a powdered material of the substrate, the first optical subsystembeing controllable so as to generate a plurality of different powerdensity levels, with a specific one of said power density levels beingselectable based on a specific material forming a powder bed being usedto form a 3D part; the first optical subsystem being able to generatethe electromagnetic radiation with an average power density level ofgreater than 200 W/cm² over the duration of the signal, and producing abeam having an area sufficient to illuminate at least a portion of thepowdered material and to melt the powdered material; and at least oneprocessor which dynamically controls the first optical subsystem, and isconfigured to adjust a power density level of the optical signal takinginto account a composition of the powdered material; and an secondoptical subsystem arranged upstream of the powdered material, anddownstream of the first optical subsystem, relative to a direction oftravel of the optical signal, the second optical subsystem beingconfigured to receive the optical signal from the first opticalsubsystem and to provide control over the optical signal to helpfacilitate melting of the powdered material in a layer-by-layer sequenceof operations.
 2. The system of claim 1, where the second opticalsubsystem comprises a relay telescope.
 3. The system of claim 1, wherethe second optical subsystem generates the optical signal with a shapeformed as a line focus.
 4. The system of claim 1, where the firstoptical subsystem is comprised of one or more optical sources forgenerating the optical signal with its own controllable power supplywhich provides control over the output power of the source.
 5. Thesystem of claim 4, where the one or more optical sources is a laser. 6.The system of claim 4, where the one or more sources comprises an arrayof diode lasers including one or more bars of diode lasers.
 7. Thesystem of claim 4, wherein the one or more optical sources comprises aplurality of optical sources, where the output of the first opticalsubsystem is an array of optical signals from each of the opticalsources, forming a 2D array.
 8. The method of claim 7, where the 2Darray is comprised of an array of lines, where each said line iscomprised of one or more optical sources.
 9. The system of claim 8,where each said source is controlled in the 2D array such that theoutput of the first optical system is an image.
 10. The system of claim9, wherein: the second optical subsystem comprises a relay telescope;and where a full 2D image from the first optical subsystem is relayed tothe powder bed by the relay telescope such that the full 2D image isincident on the powdered material and the power density is tuned to meltthe powdered material in a pattern corresponding to the full 2D image.11. The system of claim 2, where a full 2D image from the first opticalsubsystem is relayed to the powder bed by the relay telescope such thatthe full 2D image is incident on the powdered material and the powerdensity is tuned to melt the powdered material in a patterncorresponding to the full 2D image.
 12. The system of claim 9, wherein:the second optical subsystem forms a plurality of beams, each beingformed as a line focus; and wherein a full 2D image is produced by thefirst optical subsystem and relayed by the first optical subsystem tothe powder bed by the relay telescope, such that the full 2D image isincident on the powdered material and the power density is tuned to meltthe powdered material in a pattern corresponding to the full 2D image.13. The system of claim 3, wherein: one or more of the lines of the full2D image from the first optical subsystem is relayed to the powder bed;and the system further includes a second optical subsystem forming aplurality of beams, each beam of one of said plurality of beams beingformed as a line focus, such that each said beam formed as the linefocus is incident on the powdered material and the power density of thebeams is tuned to melt the powdered material in a pattern correspondingto the one or more lines.
 14. The system of claim 10, further comprisinga 2D mask configured to reside between the first and second opticalsubsystems.
 15. The system of claim 7, further comprising a 2D maskconfigured to reside between the first and second optical subsystems.16. The system of claim 14, wherein the 2D mask comprises a dynamicmask.
 17. The system of claim 14, wherein the 2D mask comprises anon-addressable mask forming a static mask.
 18. The system of claim 15,where the 2D mask comprises a dynamic mask.
 19. The system of claim 15,where the 2D mask comprises a non-addressable mask forming a staticmask.
 20. A method for performing an Additive Manufacturing (AM)fabrication process on a powdered material forming a substrate, themethod comprising: using a first optical subsystem for generating anoptical signal comprised of electromagnetic radiation sufficient to meltor sinter a powdered material of the substrate, the first opticalsubsystem being controlled so as to generate a plurality of differentpower density levels, with a specific one of said power density levelsbeing selectable based on a specific material forming a powder bed beingused to form a 3D part; the first optical subsystem being able togenerate the electromagnetic radiation with an average power densitylevel of greater than 200 W/cm² over the duration of the signal, andproducing a beam having an area sufficient to illuminate at least aportion of the powdered material and to melt the powdered material;using at least one processor to dynamically control the first opticalsubsystem, and to adjust a power density level of the optical signaltaking into account a composition of the powdered material; and using asecond optical subsystem arranged upstream of the powdered material, anddownstream of the first optical subsystem, relative to a direction oftravel of the optical signal, to receive the optical signal from thefirst optical subsystem and to provide control over the optical signalto help facilitate melting of the powdered material in a layer-by-layersequence of operations.
 21. An apparatus for performing an AdditiveManufacturing (AM) fabrication process on a powdered material forming asubstrate, the apparatus comprising: a laser source for generating alaser beam; an optical subsystem for shaping the laser beam into atleast one line segment directed at the powdered material; the lasersource being able to generate the electromagnetic radiation with anaverage power density level of greater than 200 W/cm² which providessufficient power to melt the powdered material; at least one processorwhich controls at least one of the laser source or the optical subsystemto adjust a power density level of the laser beam; and the line segmentof the laser beam used to melt different linear segments of the powderedmaterial, and repeating the melting of additional linear segments ofpowdered material in a layer-by-layer sequence of operations usingsuccessively melted layers of the powdered material to form anadditively manufactured part.
 22. An apparatus for performing anAdditive Manufacturing (AM) fabrication process on a powdered materialforming a substrate, the apparatus comprising: an optical subsystemincluding at least one laser source for producing a plurality ofsimultaneously generated laser beam line segments directed at thepowdered material; the laser source being able to generate the laserbeam with an average power density level of greater than 200 W/cm² whichprovides sufficient power to melt the powdered material; at least oneprocessor which controls the optical subsystem to help adjust a powerdensity level of the laser beam line segments; and the laser beam linesegments being used to simultaneously melt different linear segments ofthe powdered material, and repeating the melting of different linearsegments in a layer-by-layer sequence of operations using successivelymelted layers of the powdered material to form an additivelymanufactured part.